1. Field of the Invention
The present invention relates to a liquid crystal display device, and in particular to a technique for ensuring an appropriate interval between a TFT substrate and an opposed substrate, using a column-type spacer.
2. Description of the Related Art
In a liquid crystal display device, liquid crystal is filled between a TFT substrate with a pixel electrode and a thin film transistor (TFT) formed thereon and an opposed substrate with a color filter or the like formed thereon, and the liquid crystal particles are controlled by means of an electric field to thereby form an image. The interval between the TFT substrate and the opposed substrate is very small, such as of the order of a few microns. Conventionally, the interval between the TFT substrate and the opposed substrate is determined by dispersing plastic beads and the like. According to this interval setting by dispersing beads, however, the beads may not be dispersed consistently, and in such a case the interval between the TFT substrate and the opposed substrate may not be set as predetermined. In addition, the beads may be dispersed on a pixel electrode, which may cause a problem of light leakage in the vicinity of the beads.
Meanwhile, conventionally, in order to fill liquid crystal, the space between the TFT substrate and the opposed substrate is sealed to be vacant, and liquid crystal is injected into the space by utilizing atmospheric pressure. This method, however, takes time to complete injection of liquid crystal when the interval between the TFT substrate and the opposed substrate is small and the surface of the liquid crystal display is large. As a result, manufacturing throughput is reduced, and manufacturing cost resultantly increases. In order to address the above, there has been developed a technique, e.g., for applying, by dropping, the required amount of liquid crystal onto a TFT substrate and thereafter forming an opposed substrate to seal the liquid crystal in-between.
As described above, conventionally, the interval between the TFT substrate and the opposed substrate is maintained by small beads dispersed therein. However, according to the above described liquid crystal dropping method, the dispersed beads may move as the liquid crystal is dropped, which results in an area with many beads and an area with only a few beads. This results in an inconsistent interval between the TFT substrate and the opposed substrate, and an inconsistent interval between the TFT substrate and the opposed substrate in turn results in a problem of reduced image contrast and/or inconsistent pixels in a liquid crystal display device.
In order to address the above described problem with a case in which the interval between a TFT substrate and an opposed substrate is set utilizing beads, there is available a technique for defining the interval between the TFT substrate and the opposed substrate by forming a column on either the TFT substrate or the opposed substrate, as disclosed in Japanese Patent Laid-open Publication No. Hei 11-84386.
The column for defining the interval between the TFT substrate and the opposed substrate is conventionally formed on the opposed substrate. Specifically, in formation of a column on the opposed substrate, the column is formed such that, after the opposed substrate and the TFT substrate are combined to each other, the column abuts on a predetermined position on the TFT substrate. However, should the opposed substrate and the TFT substrate be displaced from each other when being combined to each other, a column resultantly abuts outside the predetermined position on the TFT substrate. This may result in a column formed on a pixel electrode or a column falling on a through-hole formed on a line of the TFT substrate. A column formed on a pixel electrode results in light leakage due to orientation disturbance in the portion where such a column is formed. A column falling on a through-hole results in an interval not appropriately defined between the TFT substrate and the opposed substrate.
Japanese Patent Laid-open Publication No. Hei 11-84386 discloses a structure in which a column is formed on either the opposed substrate or the TFT substrate in a position on a capacitance line in order to address orientation disturbance which would be caused in the vicinity of the column, and moreover, the capacitance line is laid extending in the rubbing direction of the alignment film. However, the capacitance line, which is essential in the above described structure disclosed in Japanese Patent Laid-open Publication No. Hei 11-84386, reduces transmittance of the liquid crystal display device. In particular, the capacitance line extending in the rubbing direction of the alignment film, as described in Japanese Patent Laid-open Publication No. Hei 11-84386, further reduces the transmittance.